It is entirely possible to run 100% tax rate while you are actively playing Evony. You can use comforting every 15 minutes to raise your loyalty or raise your population. “Population Raising” uses food and will give you about 5% more population. Since your loyalty will be constantly going down you’ll have to use population raising to keep your population up. When you log off you want to reset your tax rate to a reasonable number or your population will go down, people will start to revolt and riot in your city.
If you forget to reset your tax rate to a more reasonable amount and go to sleep then you may wake up to find your city is rioting because their loyalty has decreased to 0, they aren’t getting enough food, your heroes aren’t getting enough gold, etc.